Seaweed cultivation apparatus and seaweed cultivation method

Abstract

To allow efficient cultivation of seaweed by efficiently circulating the seaweed to prevent it from accumulating, when cultivating seaweed in a raceway tank.SOLUTION: The seaweed cultivation apparatus of the present invention includes a raceway-type tank for cultivating seaweed by circulating culture water, the seaweed being 3 cm or longer in length, and the apparatus including a culture water circulator that circulates the culture water, and vortex generating means that generates a vortex in the raceway-type tank. The seaweed cultivation method of the present invention uses a seaweed cultivation apparatus including a raceway-type tank for cultivating seaweed by circulating culture water, the seaweed being 3 cm or longer in length, and the apparatus including a culture water circulator that circulates the culture water, and vortex generating means that generates a vortex in the raceway-type tank.SELECTED DRAWING: Figure 3a2

Description

[Technical Field]

[0001] The present invention relates to a seaweed cultivation apparatus and a seaweed cultivation method. [Background technology]

[0002] There are two methods for cultivating seaweed: harvesting naturally growing seaweed and cultivating seaweed in a way that manages the entire process from seed production to harvesting. Seaweed has been cultivated in Asia for centuries, and in recent years its popularity has been expanding worldwide. In fiscal year 2020, the production volume of cultivated seaweed reached approximately 400,000 tons, a figure significantly higher than the 310,000 tons of shellfish and the 250,000 tons of fish (Non-Patent Document 1). Seaweed farming is also considered important from an environmental conservation perspective. Seaweed reduces carbon dioxide as it grows through photosynthesis, and it is expected to improve water quality by absorbing nitrogen from the seawater as nutrients, and also serve as a habitat for fish. However, rising seawater temperatures due to climate change can cause various problems, such as shortened cultivation periods, poor growth, and reduced production due to predation. For example, in nori (seaweed) cultivation, high water temperatures in autumn have caused delays in the start of seeding and sprout drop, resulting in reports of reduced harvests in various regions. Seaweed cultivation harvests in Japan reached 325,037 tons in 2022, a decrease of 10,807 tons (3.2%) from the previous year (Non-Patent Document 2).

[0003] Patent documents 1 and 2 show prior art methods for cultivating laver. The laver cultivation method using laver cultivation rope involves fixing laver seeds to the rope and growing them in a natural seawater environment. In this method, appropriately selected seeds are attached to the rope and placed in the sea. The rope becomes a base for the laver to grow in the sea, receiving currents and sunlight. The grown laver is harvested along with the rope, allowing for efficient large-scale production. After harvesting, the laver is washed and dried before being put on the market. However, this aquaculture method presents several challenges. For example, fluctuations in seawater temperature and abnormal weather can make the aquaculture environment unstable. This can lead to poor growth of the laver and an increased risk of disease. Damage to the ropes can also reduce harvest yields. Furthermore, it is necessary to select appropriate locations for the establishment of aquaculture farms, and depending on the location, there are challenges such as impacts on the ecosystem and conflicts of interest with the fishing industry.

[0004] Patent documents 3 and 4 show the applicant's land-based seaweed cultivation technology using circular tanks. When using the large circular tanks introduced in Patent document 4, several problems arise. For example, the paddles used to stir the entire water surface are large, and the motor installed in the center of the tank is also large, which increases the maintenance burden. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-092935 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-279044 [Patent Document 3] Patent No. 7185815 [Patent Document 4] Patent No. 7307987 [Patent Document 5] Japanese Patent Application Publication No. 8-116965 [Patent Document 6] Patent Publication No. 2015-231349 [Non-patent literature]

[0006] [Non-Patent Document 1] "Seaweed farming is booming worldwide: What are its uses other than eating it raw?", February 11, 2022, TSURINEWS, https: / / tsurinews.jp / 195373 / [Non-patent document 2] “Fisheries and Aquaculture Production Statistics for 2020”, February 29, 2020, Ministry of Agriculture, Forestry and Fisheries, https: / / www.maff.go.jp / j / tokei / kekka_gaiyou / gyogyou_seisan / gyogyou_yousyoku / r4 / Summary of the Invention [Problem to be solved by the invention]

[0007] The inventors are exploring a new method for cultivating seaweed using raceway-type tanks (hereinafter referred to as "raceway tanks"). Raceway tanks are a well-known technology that is widely used to cultivate microscopic algae such as chlorella (e.g., Patent Documents 5 and 6). However, it has become clear that various challenges arise when attempting to cultivate seaweed, which is significantly larger than microalgae, in a similar tank. 9 shows an actual photograph of seaweed being cultivated in the raceway tank 100, the photograph having been taken from above the tank. The photograph corresponds to a plan view of the tank 100. The water current generated by the water wheel (paddle) 20 installed in this tank circulates the water within the tank. It was found that large amounts of seaweed were accumulating in some areas of the raceway tank. Specifically, seaweed was accumulating in the area enclosed by the dashed line in Figure 9. Because seaweed is larger than microalgae, uneven water currents and other factors cause the seaweed to not be stirred evenly and not be dispersed in a balanced manner. Since the problem is the uneven water current depending on the location in the tank, simply increasing the power of the water wheel motor does not fundamentally solve the problem. It would be desirable to solve this problem using the stirring power of a typical water wheel. [Means for solving the problem]

[0008] The seaweed cultivation device of the present invention includes a raceway-type tank for cultivating seaweed by circulating cultivation water, and the seaweed has a length of 3 cm or more. The seaweed cultivation device is equipped with a cultivation water circulation device for circulating the cultivation water, and a vortex generating means for generating a vortex in the raceway-type tank. [Effects of the Invention]

[0009] When cultivating seaweed in a raceway tank, efficient circulation of the seaweed can prevent the seaweed from accumulating, allowing for efficient cultivation. [Brief explanation of the drawings]

[0010] [Figure 1] Seaweed Photos [Figure 2a1] Example of a raceway tank [Figure 2a2] Example of a raceway tank [Figure 2a3] Example of a raceway tank [Figure 2b] Example of a raceway tank [Figure 2c] Example of a raceway tank [Figure 2d] Example of a raceway tank [Figure 2e] Example of a raceway tank [Figure 2f] Example of a raceway tank [Figure 2g] Example of a raceway tank [Figure 2h] Example of a raceway tank [Figure 2i] Example of a raceway tank [Figure 2j1] Example of a raceway tank [Figure 2j2] Example of a raceway tank [Figure 2j3] Example of a raceway tank [Figure 2j4] Example of a raceway tank [Figure 2j5] Example of a raceway tank [Figure 2k] Example of a raceway tank [Figure 2l] Example of a raceway tank [Figure 2m] Example of a raceway tank [Figure 3a1] Example of the present invention (Example 1) [Figure 3a2] Example of the present invention (Example 1) [Figure 3b1]Example of the present invention (Example 1) [Figure 3b2] Example of the present invention (Example 1) [Figure 3b3] Example of the present invention (Example 1) [Figure 3c1] Example of the present invention (Example 1) [Figure 3c2] Example of the present invention (Example 1) [Figure 3c3] Example of the present invention (Example 1) [Figure 3c4] Example of the present invention (Example 1) [Figure 3c5] Example of the present invention (Example 1) [Figure 3d1] Example of the present invention (Example 1) [Figure 3d2] Example of the present invention (Example 1) [Figure 3d3] Example of the present invention (Example 1) [Figure 3d4] Example of the present invention (Example 1) [Figure 3e1] Example of the present invention (Example 1) [Figure 3e2] Example of the present invention (Example 1) [Figure 3f1] Example of the present invention (Example 1) [Figure 3f2] Example of the present invention (Example 1) [Figure 3f3] Example of the present invention (Example 1) [Figure 4a] Example of the present invention (Example 1) [Figure 4b] Example of the present invention (Example 1) [Figure 4c] Example of the present invention (Example 1) [Figure 4d] Example of the present invention (Example 1) [Figure 4e] Example of the present invention (Example 1) [Figure 4f1] Example of the present invention (Example 1) [Figure 4f2] Example of the present invention (Example 1) [Figure 4f3] Example of the present invention (Example 1) [Figure 4f4] Example of the present invention (Example 1) [Figure 4f5] Example of the present invention (Example 1) [Figure 4f6] Example of the present invention (Example 1) [Figure 4g] Example of the present invention (Example 1) [Figure 4h] Example of the present invention (Example 1) [Figure 5a] Example of the present invention (Example 2) [Figure 5b] Example of the present invention (Example 2) [Figure 5c1] Example of the present invention (Example 2) [Figure 5c2] Example of the present invention (Example 2) [Figure 5c3] Example of the present invention (Example 2) [Figure 5d] Example of the present invention (Example 2) [Figure 5e] Example of the present invention (Example 2) [Figure 5f1] Example of the present invention (Example 2) [Figure 5f2] Example of the present invention (Example 2) [Figure 6a1] Example of the present invention (Example 3) [Figure 6a2] Example of the present invention (Example 3) [Figure 6a3] Example of the present invention (Example 3) [Figure 6b] Example of the present invention (Example 3) [Figure 6c] Example of the present invention (Example 3) [Figure 6d] Example of the present invention (Example 3) [Figure 6e] Example of the present invention (Example 3) [Figure 6f] Example of the present invention (Example 3) [Figure 6g] Example of the present invention (Example 3) [Figure 7a] Photo of the waterwheel of the present invention [Figure 7b] Photograph of the water flow control means of the present invention [Figure 7c] Photograph of the water flow outlet of the present invention [Figure 8] Examples of the present invention (Example 1 + Example 3) [Figure 9] Raceway tanks cultivating seaweed (prior art) [Explanation of symbols]

[0011] 10 Aquarium outer wall 13 Partition Wall 16 Aquarium floor 18 Rectifier plate 20 Aquaculture water circulation equipment (water wheel, etc.) 51 Eddy current generation means / water flow regulation means 54 Water outlet 55 Water flow released from the outside of the tank to the inside 71 Water flow 72 Whirlpool 100 Raceway Tank DETAILED DESCRIPTION OF THE INVENTION

[0012] <General explanation of the embodiment> Hereinafter, an embodiment of a seaweed cultivation apparatus according to the present invention will be described with reference to the drawings. (About seaweed) The seaweed referred to in the present invention may be any kind of seaweed, and includes, for example, green laver, sea lettuce, single-grained cod, kelp, wakame, Akamoku, Sargassum chinensis, hijiki, mozuku, Japanese kelp, matsumo, tsurumo, Eisenia bicolor, Kurome, Antokume, Kayamonori, Porphyra spp., Amanori, Tosakanori, Gracilaria verrucosa, mirin, filigreed grass, tarsiram, Fusanori, Sujikonori, funori, Agar, Gingko, hornwort, centipede, Fudaraku, Tsurutsuru, Tsuzuregusa, Eucheuma, Kagikenori, dulse, Suginori, Umizomen, Yuna, Shikinori, and the like. It is desirable for the seaweed to be 3 cm or longer. This length limitation is intended to clarify that the seaweed targeted by the present invention is large seaweed, which is significantly different from microalgae of a few microns in size. More preferably, the seaweed is 5 cm or longer in length, and even more preferably, 7 cm or longer. The larger the seaweed, the more difficult it is to stir the seaweed evenly, making the effects of the present invention more pronounced. Figure 1 shows actual photographs of seaweed of various lengths. As shown in Figure 1, the length of seaweed can be determined by stretching it in a specific direction.

[0013] (About the raceway tank) Figure 2a1 is a plan view of a raceway tank 100 used in the present invention. The raceway tank is composed of an outer wall 10, a partition wall 13, and a tank floor 16. In plan view, the area surrounded by the outer wall 10 and the partition wall 13 is the circulating water channel, which is filled with aquaculture water. The partition wall 13 has circulating water channels on both sides. Figure 2a2 shows a three-dimensional view of a typical raceway tank 100. Figure 2a3 shows the raceway tank 100 filled with water. There are no particular restrictions on the depth of the culture water filled in the raceway tank of the present invention, but it is preferable that it be 600 mm or less. In plan view, the exterior wall 10 has a shape similar to an athletics racetrack, with two straight sections and two semicircular sections connecting the straight sections. A water circulation device 20, such as a water wheel (tillage machine, paddle), is installed midway along the circulating water channel. Rotating the blades of the water wheel generates a water flow in the circulating water channel. The arrows in the circulating water channel in Figure 2a1 indicate the flow of water. In Figure 2a1, the water circulates counterclockwise, but it can also be circulated clockwise as in Figure 2b(1). If a water wheel that can rotate in either direction is used, it can also be circulated counterclockwise by simply switching the direction of rotation of the motor as in Figure 2b(2). Furthermore, the number of aquaculture water circulating devices 20 used in one raceway tank is not limited to one, but may be two or more. Two aquaculture water circulating devices (water wheels) 20 are provided in the raceway tank 100 of Fig. 2c. Furthermore, unless otherwise specified, the aquaculture water circulating device 20 may be installed anywhere in the raceway tank 100. It is not limited to being installed in a straight section of the tank, but may also be installed in an arc section. In Figure 2d, the aquaculture water circulating device 20 is installed in an arc section of the tank. Furthermore, unless otherwise specified, the water flow direction may be either clockwise or counterclockwise in a plan view. The aspect ratio of the raceway tank 100 is optional. The raceway tank 100 shown in Fig. 2e may be longer than the raceway tank shown in Fig. 2a1. The size of the partition wall 13 of the raceway tank 100 can also be determined arbitrarily. The thickness of the partition wall 13 in the short side direction of Fig. 2f is thicker than that of the partition wall 13 in Fig. 2a1. Also, the partition wall 13 in Fig. 2g may have a hollow portion in plan view. At least one straight section of the raceway tank is preferably at least 10 m long, more preferably 15 m long. The ratio of the length (in the stretching direction) of the straight portion of the raceway tank to its width is preferably 3 or more, more preferably 5 or more, and even more preferably 7 or more. The effect of the present invention becomes more pronounced as the ratio increases. Figure 2a1 shows the width and length of the straight portion of the raceway tank.

[0014] The raceway tank of the present invention may have any shape as long as the tank forms a circulating water channel and a water current is generated in the circulating water channel by an aquaculture water circulator. Examples of variations in the appearance of the raceway tank 100 are shown in Figures 2h and 2i. The raceway tank 100 in FIG. 2h has four straight sections and four semicircular sections connecting the straight sections. The raceway tank 100 in FIG. 2i has six straight sections and six semicircular sections connecting the straight sections.

[0015] The names of the straight sections of the raceway tank 100 will be defined below. The first straight section located downstream of the water flow from the location where the aquaculture water circulation device 20 is installed will be called the first straight section. The second straight section located further downstream will be called the second straight section. The third straight section located further downstream will be called the third straight section. Similarly, the Nth straight section located downstream will be called the Nth straight section (see Figures 2j1 and 2j2). When multiple aquaculture water circulation devices 20 are installed in the raceway tank 100, if the straight section is the Nth straight section from the aquaculture water circulation device 20 closest to the upstream side, it is called the Nth straight section (see Figures 2j3 and 2j4). Also, as shown in Figure 2j5, an embodiment is possible in which the portions connecting the respective straight line segments are not semicircular but arcs in plan view. In Figure 2j5, arcs with a central angle of 90 degrees connect the straight line segments.

[0016] The raceway tank 100 may have a current plate 18 or the like disposed in the semicircular portion thereof to regulate the flow of water (see FIG. 2k). The outer wall 10 and the partition wall 13 of the raceway tank 100 do not necessarily have to be flat in plan view, and may have irregularities such as recesses and protrusions, distortions, or warping. Figure 2l shows an example of such recesses and protrusions. Each straight section of the raceway basin 100 has an upstream region, a midstream region, and a downstream region from the upstream of the water flow. For the sake of the following explanation, as shown in Figure 2m, a first straight section upstream region, a first straight section midstream region, a first straight section downstream region, a second straight section upstream region, a second straight section midstream region, and a second straight section downstream region will be defined.

[0017] (About aquaculture water) The culture water of the present invention is water for cultivating seaweed. Seawater is preferable, but a liquid simulating seawater may also be used.

[0018] (About the aquaculture water circulation system) The aquaculture water circulation device of the present invention generates a circulating water flow in the raceway tank. Any known device can be used as appropriate. A water wheel (paddle) is preferred. A jet water flow introduced from the outside can also be used. A photograph of an example of an aquaculture water circulation device (water wheel) is shown in Figure 7a. The speed of the water flow in the raceway tank is not particularly limited, but is generally 5 cm / sec to 5 m / sec, and preferably 10 cm / sec to 2 m / sec.

[0019] <Example 1-1> The seaweed cultivation apparatus of the present invention includes a raceway-type tank for cultivating seaweed by circulating culture water, and includes a culture water circulator for circulating the culture water and seaweed having a length of 3 cm or more, and a vortex generating means for generating a vortex in the tank. In Example 1, the vortex generating means is a water flow regulating means for regulating the water flow. The water flow control means is preferably a plate-shaped member as shown in Figure 7b, but any structure that can control the water flow, such as a beam-shaped member or a wall-shaped member, can also be used. This is the same for all other embodiments. The raceway basin 100 shown in Fig. 3a1 is provided with a water flow restriction means 51. The water flow restriction means 51 is arranged inside the outer wall 10 of the upstream region of the second straight section. Fig. 3a2 shows a three-dimensional view of the raceway basin 100. The water flowing from the first straight section to the second straight section is partially blocked by the water flow regulating means 51, and its flow path is changed as shown by water flow 71 in the figure. Downstream of the water flow regulating means 51, a vortex 72 is generated as shown in Figure 3b1, and over time, this vortex 72 moves downstream as shown in Figures 3b2 and 3b3. Eventually, the state of Figure 3b1 is restored, and a new vortex 72 is formed downstream of the water flow regulating means 51. The periodic generation of this vortex causes seaweed that has been retained in the raceway tank to begin to move, thereby alleviating the problem of seaweed retention. Note that, as shown in other embodiments, adjustments may be made so that the vortex continues to be generated primarily in the same place.

[0020] Figure 3c1 is an actual photograph of the embodiment. Figures 3c2 and 3c3 are enlarged photographs of the area surrounded by the dashed line in Figure 3c1. The water flow regulating means 51 regulates the path of water flow 71, generating vortex flow 72 downstream, improving water retention throughout the tank (particularly in the area downstream of the straight section where water flow regulating means 51 is located). In this invention, vortices can be recognized in a planar view from above the aquarium. Seaweed moves along the vortex in a trajectory that is close to a circle or ellipse. The occurrence of a vortex can be recognized by taking a video of the moving seaweed in a planar view from above. The size of the vortex can also be determined from photographs or videos taken from above, as shown in Figure 3c3. In Figure 3c3, a circular vortex with a diameter of at least 80% or more of the width of the straight section can be confirmed. Figures 3c4 and 3c5 are photographs of the raceway tank 100 taken from above after a certain time has elapsed from a reference time. (1) is a photograph taken at a certain reference time (t=0 s), (2) is a photograph taken 20 seconds after the reference time, (3) is a photograph taken 40 seconds after the reference time, and (4) is a photograph taken 60 seconds after the reference time. (5) is a photo taken 80 seconds after the reference time. (6) is a photo taken 100 seconds after the reference time. (7) is a photo taken 120 seconds after the reference time. From the photograph in Figure 3c4, it is possible to grasp the location and size of the vortex 72 occurring in the water flow restriction means 51. It can be seen that the vortex moves gradually downstream with the passage of time. A vortex is also generated upstream of the water flow regulating means 51. Because the width of the water flow is narrowed by the water flow regulating means 51, a portion of the water flow that cannot flow through slowly swirls upstream of the water flow regulating means 51. The vortex 72 does not always occur in the same place and with the same shape, but its size and location are constantly changing, as shown in Figure 3c4. From the photograph in Figure 3c5, it is possible to see how the seaweed in the raceway tank 100 moves over time. In this raceway tank, the area surrounded by the dashed line in the photograph in Figure 3c5(1) is an area where seaweed would likely become trapped if the water flow restriction means 51 were not present (see Figure 9). The vortex created by the water flow restriction means 51 allows the seaweed in this area to move smoothly downstream over time. Retention has been improved throughout the tank (especially in the area downstream of the straight section where the water flow restriction means 51 is located). In this embodiment, a vortex is generated downstream of the vortex generating means 51 (water flow restricting means 51) for at least 5 seconds, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 60 seconds, 80 seconds, 100 seconds, or 120 seconds. The size of this vortex (width in the direction perpendicular to the water flow direction) is 40% or more of the width of the straight section of the raceway water tank.

[0021] <Example 1-2> The water flow control means 51 may be installed anywhere in the raceway tank, and the location should be selected appropriately depending on where the seaweed is staying. Figure 3d1 is an illustration of the raceway tank 100 when the water flow control means 51 is placed on the partition wall 13 in the midstream region of the first straight section. As in Example 1-1, the water flow control means 51 controls the path of the water flow 71, generating a vortex 72. The vortex can move seaweed that has accumulated in the tank by entraining it in the water current. Figures 3d2 and 3d3 are photographs of the raceway tank 100 taken from above after a certain time has elapsed from a reference time. (1) is a photograph taken at a certain reference time (t=0 s), (2) is a photograph taken 15 seconds after the reference time, (3) is a photograph taken 30 seconds after the reference time. Water flow control means 51 was installed 30 seconds after the reference time, (4) is a photograph taken 40 seconds after the reference time, (5) is a photograph taken 60 seconds after the reference time, (6) is a photograph taken 80 seconds after the reference time, and (7) is a photograph taken 100 seconds after the reference time. After the water flow control means 51 is installed (3), a vortex 72 occurs. The vortex gradually grows larger, and as shown in Figure 3d2 (6) and (7), a vortex may also occur upstream of the water flow control means 51. From the photograph in Figure 3d3, it is possible to see how the seaweed in the raceway tank 100 moves over time. In this raceway tank, the area surrounded by the dashed line in the photograph in Figure 3d3(1) is an area where seaweed would likely become trapped if the water flow control means 51 were not present (see Figure 9). The vortex created by the water flow control means 51 allows the seaweed in this area to move smoothly downstream over time. In the photograph in Figure 3d3(7), the seaweed trapping has almost completely disappeared. In the embodiment shown in Fig. 3d2, a vortex is generated downstream of the vortex generating means 51 (water flow restricting means 51) for at least 5 seconds, 10 seconds, 20 seconds, 30 seconds, 40 seconds, or 60 seconds. The size of this vortex (width in the direction perpendicular to the water flow direction) is 40% or more of the width of the straight section of the raceway water tank. Figure 3d4 shows an embodiment in which the water flow control means 51 is moved slightly upstream from the embodiment in Figure 3d3. As in this embodiment, two or more vortexes 72 may be generated. Note that in photographs of other embodiments, two or more vortexes may be generated, but this is not necessarily shown. In the embodiment shown in Figure 3d4, a vortex is generated downstream of the vortex generating means 51 (water flow restricting means 51) for at least 5 seconds, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 60 seconds, 80 seconds, 100 seconds, or 120 seconds. The size of this vortex (width in the direction perpendicular to the water flow direction) is 40% or more of the width of the straight section of the raceway tank.

[0022] <Examples 1-3> FIG. 3e1 is an illustration of the raceway basin 100 in which the water flow restriction means 51 is disposed on the outer wall 10 in the midstream region of the second straight section. Figure 3e2 is a photograph of the raceway tank 100 taken from above after a certain time has elapsed since the reference time. (1) is a photograph taken at a certain reference time (t=0 s). Water flow restriction means 51 was installed at this reference time. (2) is a photograph taken 30 seconds after the reference time. (3) is a photograph taken 60 seconds after the reference time. (4) is a photograph taken 90 seconds after the reference time. A vortex 72 is generated downstream of the water flow regulating means 51. A faint vortex 72 is also generated upstream of the water flow regulating means 51. The generation of such a vortex improves the retention of seaweed throughout the aquarium (particularly in the area downstream of the straight section where the water flow regulating means 51 is located). In the embodiment of Fig. 3e2, a vortex is generated downstream of the vortex generating means 51 (water flow restricting means 51) for at least 5 seconds, 10 seconds, 20 seconds, 30 seconds, 60 seconds, or 90 seconds. The size of this vortex (width in the direction perpendicular to the water flow direction) is 40% or more of the width of the straight section of the raceway water tank.

[0023] <Examples 1-4> FIG. 3f1 is an illustration of a case where the water flow regulating means 51 is disposed on the outer wall 10 in the downstream region of the second straight section. Figure 3f2 is an actual photograph of this example. Figure 3f3 is an enlarged photograph of the area surrounded by the dashed line in Figure 3f2. The water flow restriction means 51 generates a vortex 72 downstream, improving the retention of seaweed throughout the tank (especially in the area downstream of the straight section where the water flow restriction means 51 is located).

[0024] <Examples 1-5> A further example of a variation of the embodiment of the present invention will be described. FIG. 4a is an illustration of a case where the water flow regulating means 51 is disposed on the partition wall 13 in the upstream region of the second straight section. FIG. 4b is an illustration of a case where the water flow regulating means 51 is disposed on the partition wall 13 in the midstream region of the second straight section. FIG. 4c is an illustration of a case where the water flow regulating means 51 is disposed on the outer wall 10 in the midstream region of the first straight section. The water flow control means 51 can be placed in various locations in the raceway tank where seaweed tends to accumulate. Furthermore, since large seaweed tends to accumulate in the straight sections of the raceway tank, it is desirable to install the water flow control means 51 in the straight sections of the raceway tank.

[0025] <Examples 1-6> The water flow control means 51 is not limited to the rectangular members shown above, and may be any shape as long as it generates a large vortex by controlling the flow of water. It may be a plate-like member, a beam-like member, a wall-like member, or any other structure. Figures 4d and 4e show other examples of the water flow restriction means 51. In Figure 4d, the water flow restriction means 51 has a triangular shape in plan view. In Figure 4e, the water flow restriction means 51 has an arc-like shape in plan view. Of course, the water flow restriction means 51 with these shapes can also be installed anywhere in the raceway tub 100.

[0026] <Examples 1-7> 4f1 to 4f6 show examples of arrangements in which two or more water flow regulating means 51 are used. In the embodiment of FIG. 4f1, two water flow restriction means 51 are used, which are installed on the partition wall 13 in the midstream region of the first straight section and on the outer wall 10 in the upstream region of the second straight section, respectively. In the embodiment of FIG. 4f2, two water flow restriction means 51 are used, which are respectively installed on the outer wall 10 in the upstream region of the second straight section and on the partition wall 13 in the midstream region of the second straight section. In the embodiment of FIG. 4f3, two water flow restriction means 51 are used, which are respectively installed on the outer wall 10 in the upstream region of the second straight section and on the outer wall 10 in the downstream region of the second straight section. In the embodiment of Figure 4f4, three water flow regulating means 51 are used, which are installed respectively on the partition wall 13 in the midstream region of the first straight section, the outer wall 10 in the upstream region of the second straight section, and the outer wall 10 in the downstream region of the second straight section. In the embodiment of Figure 4f5, three water flow regulating means 51 are used, which are installed on the outer wall 10 in the upstream region of the second straight section, the partition wall 13 in the midstream region of the second straight section, and the outer wall 10 in the downstream region of the second straight section, respectively. In the embodiment of Figure 4f6, four water flow regulating means 51 are used, which are installed respectively on the partition wall 13 in the midstream region of the first straight section, the outer wall 10 in the upstream region of the second straight section, the partition wall 13 in the midstream region of the second straight section, and the outer wall 10 in the downstream region of the second straight section. The number and installation locations of the water flow control means 51 can be selected in various ways depending on the location where the seaweed accumulates.

[0027] <Example 1-8> Figure 4g shows an example using a raceway tank with three or more straight sections. The number and installation locations of the water flow control means 51 can be selected in various ways depending on the location where the seaweed accumulates.

[0028] <Variations of Example 1> 4h shows the installation angle Θ of the water flow control means 51 in a plan view. The angle formed between the direction of the water flow and the plate surface of the water flow control means 51 in the extension direction is defined as the installation angle Θ of the water flow control means 51. The installation angle of the water flow regulation means 51 is preferably 15 degrees or more and 90 degrees or less, more preferably 30 degrees or more and 90 degrees or less, and even more preferably 45 degrees or more and 80 degrees or less. In a plan view of the water flow control means 51, the length perpendicular to the direction of the water flow is defined as the width WB of the water flow control means 51 (see FIG. 4h). The width WB of the water flow control means 51 is preferably 10 to 80% of the width P of the straight section of the raceway basin 100, and more preferably 10 to 60%. Here, if the width is too small, sufficient vortex flow cannot be generated. If the width is too large, the water flow will be poor and inefficient. The same applies to the water flow control means of any shape shown in Examples 1-6. The size of the vortex can be adjusted by appropriately selecting the shape and size of the water flow restriction means 51. The shape of the vortex is sufficient as long as it is loop-like. Typically, it is a circle or an ellipse, but is not limited to these. In a plan view of the vortex, the length perpendicular to the direction of the water flow is defined as the width WU of the vortex. The width WU of the vortex is desirably 40 to 100% of the width P of the straight section of the raceway tank 100. It is more desirably 50 to 100%. It is more desirably 60 to 100%. It is more desirably 80 to 100%.

[0029] <Example 2> The seaweed cultivation apparatus of the present invention includes a raceway-type tank for cultivating seaweed by circulating culture water. The seaweed contains seaweed having a length of 3 cm or more, and includes a culture water circulation device for circulating the culture water, and vortex generating means for generating vortexes in the tank. In Example 2, the vortex generating means is a water flow outlet for discharging water from the outside of the raceway-type tank to the inside. The water forcefully discharged from the water flow outlet generates vortexes in the raceway tank. Water in the tank that has been discharged to the outside may also be discharged from the water flow outlet. A water flow outlet 54 is provided on the outer wall 10 of the raceway tank 100 in the upstream region of the second straight section shown in Figure 5a, and water is forcefully discharged from the water flow outlet 54 into the interior of the tank (water flow 55). This forcefully discharged water flow 55 generates a vortex 72 downstream. This vortex 72 causes seaweed that has been retained in the raceway tank to start moving, thereby alleviating the problem of seaweed retention. The discharge angle Θ of the water stream 55 is defined as the angle between the direction of the water stream flowing through the raceway tank and the direction of the water stream 55 immediately after it is discharged from the water stream discharge port 54 (see Figure 5a). Note that the water stream 55 has a certain width, and in some cases the water is injected with some spread, so the direction of the water stream 55 is considered to be the direction of the center of the width of the water stream 55. An actual photograph of the water jet outlet 54 is shown in Figure 7c. In Figure 7c, the water jet outlet 54 is installed near the floor of the tank, but it may also be installed above the floor near the water surface. The water jet outlet 54 may be detachable from the raceway tank. The example of Figure 7c is not limiting, and a hose or the like may also be used as the water jet outlet 54. The water jet outlet may be any device that corresponds to the outlet of a means that can forcefully discharge a water jet.

[0030] FIG. 5b shows variations in the installation locations of the water flow outlets 54 and the water flow 55 released therefrom. Although FIG. 5b shows ten water flow outlets 54, it is not necessary to provide all of them at the same time. This figure merely shows examples of installation locations of the water flow outlets 54. Furthermore, the installation locations are not limited to this example, and the outlets can be installed in various locations on the outer wall 10 and partition wall 13 of the raceway tank 100 depending on the location where the seaweed accumulates. The location from which the water flow 55 is released may be one location, or two or more locations. The water currents 55 discharged from the outside to the inside of the tank can be placed in various locations in the raceway tank where seaweed tends to accumulate.

[0031] Figure 5c1 is an actual photograph of an embodiment, in which a water flow 55 is emitted from the outside of the tank to the inside of the tank through a water flow outlet 54 near the boundary between the upstream and midstream regions of the second straight section. The water flow 55 is emitted at an angle of 90 degrees. Figure 5c2 is an enlarged photograph of the area surrounded by the dashed line in Figure 5c1. FIG. 5c3 is a photograph of the raceway tank 100 taken from above after a certain time has elapsed from the reference time. The water flow 55 discharged from the outside to the inside generates a vortex 72 downstream, improving the retention of seaweed throughout the tank (especially in the area downstream of the straight section where the water flow outlet 54 is located). In the example of Fig. 5c3, a vortex is generated downstream of the water flow outlet 54 for at least 5 seconds, 10 seconds, 20 seconds, 30 seconds, 40 seconds, or 60 seconds. The size of this vortex (its width in the direction perpendicular to the water flow direction) is 40% or more of the width of the straight section of the raceway water tank.

[0032] Fig. 5d shows an embodiment in which the discharge angle of the water flow 55 is 135 degrees. Fig. 5e shows an embodiment in which the discharge angle of the water flow 55 is 45 degrees. In both embodiments, a vortex 72 is generated downstream of the water flow 55.

[0033] Figures 5f1 and 5f2 are photographs of yet another embodiment. Water flow 55 is discharged from the outside of the tank to the inside through water flow outlet 54 near the boundary between the upstream region and the midstream region of the second straight section. As in this embodiment, adjustments may be made so that two or more vortices 72 are generated.

[0034] The water flow from the outside to the inside of the tank must be strong enough to generate a vortex inside the tank. Although it depends on the shape and size of the tank, a water flow of at least 100 liters per minute is desirable.

[0035] The discharge angle of the water flow 55 is preferably 30 degrees or more and 135 degrees or less. The size of the vortex can be adjusted by appropriately selecting the size of the water flow 55, the water pressure, etc. The shape of the vortex is sufficient as long as it is a loop-like shape. Typically, it is a circle or an ellipse, but is not limited to these. In a plan view of the vortex, the length perpendicular to the direction of the water flow is defined as the width WU of the vortex. The width WU of the vortex is desirably 40 to 100% of the width P of the straight section of the raceway tank 100. It is more preferably 50 to 100%. It is more preferably 60 to 100%. It is more preferably 80 to 100%. Furthermore, similar to the first embodiment, this embodiment can also be applied to a raceway tank having three or more straight sections.

[0036] Example 3 The aquaculture water circulation device of Example 3 is a water wheel with blades that stir the aquaculture water, and the water wheel not only serves as an aquaculture water circulation device but also as a vortex generating means. The asymmetric shape of the water wheel's blades causes the water that passes through the water wheel to move at an angle, generating a vortex in the tank. If the water turbine is placed on the straight section, the effect becomes even more pronounced as the water flows at an angle to the direction of extension of the straight section.

[0037] An example of a water turbine 20 capable of generating a vortex flow in a water tank as described above is shown in Figs. 6a2, 6b, 6c, 6d, 6e and 6f. The blades of the water turbine 20 in Figure 6a2 have a spiral shape. In a normal water turbine, the joint between the flat blade and the water turbine's rotating shaft extends along the extension direction of the rotating shaft, but in the case of a spiral-shaped blade, the joint between the blade and the rotating shaft extends at an angle from the extension direction of the rotating shaft, as shown in Figure 6a2. Even if the joint with the rotating shaft extends along the extension direction of the rotating shaft, the blades of the water turbine can be made spiral-shaped by slightly varying the connection angle between the blade and the rotating shaft. Figures 6a2(1) and (2) have opposite spiral twists. Figure 6a1 is an illustration of the water turbine 20 of Figure 6a2(1) placed in a raceway basin 100. The surface of the blades can be smoothly curved. The blades of the water turbine in this embodiment have an asymmetrical shape. Here, asymmetrical means that when the blades of the water turbine installed in the water basin are viewed in a plan view, they are asymmetric with respect to a center line that is perpendicular to the extension direction of the rotation axis and passes through the center of the rotation axis of the area where the blades are formed (see Figure 6a3). Among water turbines that use blades with such asymmetrical shapes, a water turbine that can generate a vortex in the water basin is the vortex generating means of the present invention. A water turbine using blades with such asymmetrical shapes can generate a vortex in the water basin because the water passing through the water turbine moves at an angle.

[0038] Figure 6b shows an example in which two spiral blades like those in Figure 6a2 are connected in series. The blades of this water turbine have an asymmetrical shape as a whole. Figure 6c shows an example of a water turbine 20 with blades of different shapes on the left and right. The left half of the water turbine 20 in Figure 6c has ordinary flat blades (three blades in the figure), and the right half has spiral blades as shown in Figure 6a2 (six blades in the figure). The blades of this water turbine have an asymmetrical shape overall. Figure 6d shows an example of a water turbine 20 with blades of different shapes on the left and right sides. The left half of the water turbine 20 has four blades, and the right half has eight blades. The blades of this water turbine have an asymmetrical shape overall. Figure 6e shows an example of a water turbine 20 with blades of different shapes on the left and right sides. The left half of the water turbine 20 has six blades, and the right half also has six blades, but the blades on the right half include blades that are larger than the other blades. In the figure, large and small blades are arranged alternately. Although not specifically shown, all blades may be large. The blades of such a water turbine have an asymmetrical shape overall. In a water turbine using such asymmetric blades, the water passing through the turbine moves at an angle from the direction of the straight section, which can generate vortexes in the water tank.

[0039] Figure 6f is a photograph of an example. Like the example in Figure 6c, this example has flat blades on the left half and spiral blades on the right half. There are three flat blades in total and six spiral blades in total. Figure 6g shows a photograph of seaweed being cultivated using the water turbine 20 of this embodiment. Three vortices 72 were observed in the first straight section downstream of the water turbine 20. A vortex 72 was also observed upstream of the second straight section further downstream. The generation of these vortices improved retention throughout the tank. Furthermore, this embodiment can also be applied to a raceway tank having three or more straight sections, similar to the second and third embodiments.

[0040] The above-described embodiments may be implemented either alone or in combination. For example, the culture water circulating apparatus of the first or second embodiment may be replaced with the culture water circulating apparatus of the third embodiment. Furthermore, the water flow regulation means 51 of Example 1 may be used in combination with the water flow outlet for discharging water into the raceway tank of Example 2 as a vortex generating means. Furthermore, the aquaculture water circulating device of Example 3 may be combined. Figure 8 shows an illustration of a raceway tank 100 equipped with water flow regulation means 51 and a water wheel 20 with spiral blades.

[0041] The content described above also relates to a seaweed cultivation method using the seaweed cultivation device. The seaweed cultivation method using the seaweed cultivation device of the present invention can also be described as follows. (Appendix 1) A seaweed cultivation method using a raceway-type water tank, a vortex generating means, and a cultivation water circulating device, The seaweed is 3 cm or longer in length, circulating the culture water in the raceway-type tank by the culture water circulating device; Seaweed is cultivated by generating a vortex in the raceway-type tank using the vortex generating means. method. (Appendix 2) The method according to claim 1, wherein the width of the vortex flow in a plan view is 40% or more of the width of the water channel of the raceway-type water tank. (Appendix 3) The method according to claim 1, wherein the aquaculture water circulating device is a water wheel having blades that stir the aquaculture water. (Appendix 4) The vortex generating means is a water flow regulating means, and the water flow regulating means regulates the direction of the water flow in the raceway-type water tank, thereby generating a vortex (Supplementary Note 1). (Appendix 5) The method according to claim 4, wherein the water flow regulating means is a plate-like member, a beam-like member, or a wall-like member installed in a straight section of the raceway-type water tank. (Appendix 6) The method according to claim 1, wherein the vortex generating means is a water flow outlet, and a vortex is generated by discharging water from the water flow outlet into the raceway-type water tank. (Appendix 7) The water turbine is also the vortex generating means, The method according to claim 3, wherein the asymmetric shape of the blades of the water turbine causes the water flow passing through the water turbine to incline, thereby generating a vortex in the raceway-type water tank.

[0042] The illustrations in the drawings shown so far are merely schematic illustrations, and the scale of the dimensions of the actual structure does not necessarily match the scale of the drawings. Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

Claims

1. A seaweed cultivation device including a raceway-type tank for cultivating seaweed by circulating cultivation water, The seaweed is 3 cm or longer in length, a culture water circulating device that circulates the culture water; a vortex generating means for generating a vortex in the raceway-type water tank; A seaweed farming device comprising:

2. 2. The seaweed cultivation apparatus according to claim 1, wherein the width of the vortex in a plan view is 40% or more of the width of the waterway of the raceway-type tank.

3. 2. The seaweed cultivation apparatus according to claim 1, wherein the culture water circulating device is a water wheel having blades that stir the culture water.

4. 2. The seaweed cultivation apparatus according to claim 1, wherein the vortex generating means is a water flow regulating means for regulating the direction of the water flow in the raceway-type water tank.

5. 5. The seaweed cultivation apparatus according to claim 4, wherein the water flow regulating means is a plate-like member, a beam-like member or a wall-like member installed in a straight portion of the raceway-type water tank.

6. 2. The seaweed cultivation apparatus according to claim 1, wherein the vortex generating means is a water flow outlet that discharges water from the outside to the inside of the raceway-type water tank.

7. The water turbine is also the vortex generating means, The seaweed cultivation device according to claim 3, wherein the asymmetric shape of the blades of the water turbine causes the water flow passing through the water turbine to move at an angle, thereby generating a vortex in the raceway-type tank.

8. A seaweed cultivation method using the seaweed cultivation apparatus according to any one of claims 1 to 7.

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